Typically, wheels for two-wheeled vehicles such as e.g. bicycles or motorcycles consist of a tire which is mounted onto a rim, and a hub which is arranged in the center of the wheel. Rim and hub are connected to each other by means of spokes or discs. The hub itself comprises a hub body, with the spokes or discs being attached to its outside, and an internally arranged axis, around which the hub body which usually runs on ball bearings can rotate freely.
The axis is connected to the bicycle by attaching its two ends, with the hub body in between, to the dropouts of the fork or the chainstays. Thus, one part of the wheel (the axis) is firmly attached to the frame, while another part (hub body with rim) can rotate.
For the fixation of the hub between the dropouts, various constructions are known.
Simple solutions provide a solid axle which runs through the hub, having threads on both ends. Further, the solid axle has shoulders, fabricated by turning or provided by counter-nuts, which lie flat against the inner sides of the dropouts. The dropouts are clamped between outside nuts and the respective shoulder by means of tightening these outside nuts, so that the desired fixation is achieved. A disadvantage of these solutions is the often heavy weight, together with the time requirement for detachment using a tool. By using wing nuts, it is possible to omit the necessity to carry along a tool when travelling; however, the risk of injury is higher then since the wing nuts laterally extend from the axle region.
In order to decrease the time necessary for attaching or detaching the hub, so called quick-release systems are known from the art. As a main component, these systems provide a usually rather thin, internally arranged tension axle, with a clamping lever with eccentric cam being attached to its one end. In direction to the hub, a pressure disc lies flat against the eccentric cam, the pressure disc providing a first clamping surface that points towards the dropout. At the second end, a thread is present onto which a counter piece can be screwed. The counter piece provides a second clamping surface which is directed contrary to the first clamping surface. By turning the clamping lever, the pressure disc is pushed in direction of the second end. Both clamping surfaces approach each other. Since they lie flat against the outsides of the dropouts, and since a fixed hollow axle of the hub through which the tension axle can be inserted is arranged between the dropouts, the hollow axle is clamped between the inner sides of the dropouts. For declamping, the opposite steps are carried out. For detachment of the hub, the dropouts usually have slot-like recesses which point downwards, so that the tension axle can remain in the hollow axle when the wheel is removed. In other cases (when having bores in the dropouts), the tensile axle must be pulled out of the hollow axle after having released the counter piece.
In cases when the stability of the fork or the chainstays must be exceptionally high, e.g. when using suspension forks or rear suspensions, said bores are preferred to slot-like recesses. The then called thru axles are inserted through the opening in the first dropout, the hollow axle of the hub, and eventually through the opening of the second dropout. Finally, a fixation is necessary. In the simplest case, this occurs by screwing a counter piece onto the second end of the axle, or by providing a thread inside the bore of the second dropout into which the thru axle can be screwed with its second end. However, this practice is time consuming and therefore particularly disadvantageous in the racing domain where shortest possible exchange times are most desirable.
Therefore, quick release systems are known also for said thru axles which shall allow for a tool-free and quick fixation and detachment of the wheel.
In document GB 2 414 971 A, a quick release system is disclosed which has a locking mechanism of the bayonet catch type at its second end. By rotating the thru axle around its longitudinal axis, e.g. for 90 degrees, the second end is locked in the counter piece; by a contrary rotation, it is unlocked again. A comparable construction is disclosed in document AU 2014271226 A1. If, however, the opening in the counter piece soils, which is particularly common in mountain biking, the operability of the locking mechanism can be limited. Further, the construction of a bayonet catch does require that axle and counter piece are inserted one into the other in a certain position in order to allow for interlocking. Usually, this position is found out by trial which is time consuming. Markers that are provided for finding the correct position can easily be soiled and thus become poorly visible.
Another solution is proposed in document WO 2009 153 038 A1. Here, the thru axle does not require a counter piece, but contains all components which are relevant for the functioning. It has a multiple slotted region at its second end, which is expandable by axial tensioning. The tensile forces are provided by means of turning the lever and via a tensile axle which is guided through the hollow axle. In the expanded state, the second end does not fit through the opening of the according dropout any more, so that clamping of the hollow axle between the inner sides of the dropouts is enabled. The expandable region can also be present at both ends of the thru axle, as disclosed in document US 2005/0110335 A1.
A comparable and also single piece solution is disclosed in document US 2009/140571 A1. Here as well, a wreathlike region is present which, in the basic state, extends over the diameter of the thru axle, therefore preventing the axle from being pulled out of the second dropout, but providing the second clamping surface instead. Upon compression with an end sleeve, this region is reduced in its diameter down to the diameter of the thru axle, so that then, a pulling out of the dropouts and the thru axle of the hub becomes possible. Here, it is necessary that the inner diameter of the openings of the dropouts as well as the diameter of the hollow axle of the hub remain approximately similar. If the diameter would increase, the wreathlike region would fan out again, since compression becomes impossible when the region, and with it, the end sleeve, are unreachable from the outside. In order to circumvent this problem, the sleeve can be fixed in the compressed state by means of rotation; then, the wreathlike region keeps the reduced diameter. However, adjusting the correct rotation angle which results in a fixation requires certain finesse. Further, the mechanics which is used for the fixation is sensitive to soiling. Also, the inner construction is rather complicated.